The present invention relates generally to laser systems and associated lasing methods and, more particularly, to modularized laser systems employing optical fiber amplifiers and associated modularized lasing methods.
Lasers are presently employed for a wide variety of applications. For example, lasers are employed to process materials, such as by cutting, welding, heat treating, drilling, trimming and coating materials. Lasers are also employed to strip paint, remove coatings, clean surfaces and provide laser markings. Lasers can also be directly applied, such as via single mode optical fibers, for a variety of medical and other applications.
Lasers are also increasingly employed in military applications, including laser weapon and laser ranging systems and electro-optical countermeasure systems. Laser communication systems have also been developed. In one more specific application, lasers can produce plasma on an illuminated surface, such as a metallic, oxide, composite, liquid or gaseous surface. The production of plasmas on the illuminated surface can produce x-rays, such as the x-rays employed in x-ray lithography.
Along with the ever increasing number of applications in which lasers are used, the demands on the laser systems are also increasing. For example, a number of applications are demanding laser systems be relatively rugged, lightweight, capable of operating in different environmental conditions, maintainable and serviceable without incurring excessive cost or experiencing prolonged downtime. In addition, laser systems are now being required to continue to operate with little degradation on a system level as components or portions of the laser system fail or otherwise become inoperative. In other words, some laser systems are required to be relatively immune on a system level to the failure of components or portions of the laser system. A number of applications are also demanding that the laser systems have little, if any, thermal signature and require little, if any, input power or power generation during operation such that the laser systems can operate independently in a manner which is relatively undetectable.
Notwithstanding the increasing demands being placed upon laser systems, laser systems must also be readily manufacturable such that the cost of the laser systems are competitive. As such, laser systems are preferably scalable so as to provide a wide range of output power levels from moderate power levels to the increasingly higher power levels demanded by some modern applications. While a variety of laser systems have been developed in order to service various ones of the applications described above, few, if any, of the conventional laser systems are readily manufacturable in such a manner that the resulting laser system is scalable so as to provide a wide range of output power levels while at the same time being relatively immune to degradation, at a system level, as a result of the failure of components of the laser system and while generating little, if any, thermal signature and requiring little, if any, power input or power generation during operation.
According to the present invention, a modularized fiber optic laser system and an associated optical amplification module are provided. As a result of the modularized design, the fiber optic laser system of the present invention is readily manufacturable and is scalable so as to provide a wide range of output power levels. The modularized design also permits the fiber optic laser system to be relatively immune, at a system level, to the failure of one or more of the optical amplification modules such that the performance of the fiber optic laser system degrades only a little, if at all, as a result of the failure of an optical amplification module. In addition, the modularized design permits the cooling, power and control functions of the fiber optic laser system to be both distributed and simplified. As a result, the optical amplification modules can operate independently without producing a thermal signature or without requiring power input or power generation during operation.
The modularized fiber optic laser system of the present invention includes at least one master oscillator for producing a master laser signal and a plurality of independent optical amplification modules that receive a portion of the master laser signal from the master oscillator. Each optical amplification module includes a plurality of optical fiber amplifiers for receiving and amplifying respective portions of the master laser signal and at least one pump source associated with each optical fiber amplifier for pumping the respective optical fiber amplifier. The optical amplification module also includes a power source, such as a battery, for providing power to the pump sources.
Each optical amplification module preferably consumes no more than a first predetermined amount of power during operation. As such, the power source is adapted to provide at least a first predetermined amount of power without recharging and without power generation. In embodiments in which the power source is a battery, for example, the battery is preferably adapted to provide at least as much power as the optical amplification module is designed to consume during operation. As such, each optical amplification module can be operated without receiving external power and without requiring power generation during operation. However, each optical amplification module can also include a battery charger for charging the battery during periods in which the optical amplification module is inactive.
Each optical amplification module is also designed to produce no more than a first predetermined amount of heat during operation. The optical amplification module of one advantageous embodiment therefore includes temperature control means for receiving and storing at least the first predetermined amount of heat such that the optical amplification module can be operated without creating a thermal signature.
According to one advantageous embodiment, the temperature control means is a heat sink having a thermal mass sufficient to store the heat which will be generated during operation of the optical amplification module. Each optical amplification module can also include a housing in which the optical fiber amplifiers, the pump source, the power source and the temperature control means are disposed. As such, the temperature control means of this embodiment can include a coolant that at least partially fills the housing such that the plurality of optical fiber amplifiers, the pump sources and the power source are immersed in the coolant. In one embodiment, the coolant includes a micro-encapsulated phase change material.
The modularized fiber optic laser system can also include a beam combiner for receiving and combining the amplified portions of the master laser signal from the plurality of optical fiber amplifiers. The modularized fiber optic laser system can also include a plurality of phase modulators, associated with respective ones of the optical fiber amplifiers, for controllably adjusting the phase of the respective amplified laser signal.
The modularized fiber optic laser system of the present invention also preferably includes means for controlling each of the optical amplification modules and/or the master oscillator based upon the output of the modularized fiber optic laser system. According to this embodiment, the modularized fiber optic laser system can include a detector for detecting a sample of the amplified portion of the master laser signal output by a respective optical amplification module. The optical amplification module can, in turn, include a controller for controlling operation of the optical amplification module in response to a signal from the detector. Similarly, the modularized fiber optic laser system can include a detector for detecting a sample of the combined output of the plurality of optical amplification modules associated with a respective master oscillator. The modularized fiber optic laser system of this embodiment can therefore also include a master oscillator controller for providing control signals to the respective master oscillator in response to a signal from the detector. By appropriately controlling the master oscillators and the plurality of optical amplification modules, the output of the modularized fiber optic laser system can be precisely controlled in both amplitude and phase and can be steered, if so desired.
As a result of the modularized design, the fiber optic laser system of the present invention is therefore readily manufacturable and is scalable so as to provide a wide range of output power levels suitable for a wide variety of applications. The modularized design also permits the fiber optic laser system to be relatively immune, at a system level, to the failure of one or more of the optical amplification modules such that the performance of the fiber optic laser system degrades only a little, if at all, as a result of the failure of an optical amplification module. In addition, the modularized design permits the cooling, power and control functions of the fiber optic laser system to be both distributed and simplified. As a result, the optical amplification modules can operate independently without producing a thermal signature or without requiring power input or power generation during operation.
FIG. 1 is a block diagram illustrating the components of one embodiment of a modularized fiber optic laser system of the present invention.
FIG. 2 is a more detailed block diagram of one of the master oscillators of the modularized fiber optic laser system of FIG. 1 as well as an associated optical amplification module.
FIG. 3 is a block diagram of an optical amplification module according to one embodiment of the present invention.
FIG. 4 is a fragmentary perspective view of the optical amplification module of FIG. 3.
FIG. 5 is a schematic diagram of one of the fiber laser amplifier circuit boards of the optical amplification module of FIGS. 3 and 4 which illustrates the optical fiber amplifiers and the associated phase modulators and pump sources.
FIGS. 6A and 6B are schematic diagrams of a single pump module and a dual pump module, respectively, for pumping an optical fiber amplifier of an optical amplification module according to one embodiment of the present invention.